Conventionally, a heat storage system for a vehicle storing engine coolant while retaining heat has been known that includes a heat accumulator, in which the engine coolant is stored and allowed to flow, in an engine coolant circulation circuit connecting an engine and a radiator (for example, Japanese Patent Application Publication No. Hei 11-182307).
In the conventional heat storage system for a vehicle, the engine coolant which has become high in temperature during driving of the vehicle is taken into the heat accumulator, and the high-temperature engine coolant is stored while retaining heat in the heat accumulator during stopping of the vehicle. Then, at the next start of the engine, the high-temperature engine coolant in the heat accumulator is sent to the engine to be used for an early warm-up of the engine.